Salts, aqueous liquid compositions containing salts of abscisic acid analogs and methods of their preparation

ABSTRACT

The present invention generally relates to salts of abscisic acid analogs, aqueous liquid compositions containing salts of analogs of abscisic acid and methods of their preparation for agricultural use.

FIELD OF THE INVENTION

The present invention generally relates to salts of abscisic acidanalogs, aqueous liquid compositions containing salts of abscisic acidanalogs and methods of their preparation for agricultural use.

BACKGROUND OF THE INVENTION

Abscisic acid is a naturally occurring plant hormone which actsprimarily to inhibit growth of plants, maintain dormancy of buds,inhibit fruit-ripening, activate the pathogen resistance responsedefense, induce senescence in already-damaged cells and their proximateneighbors, and help the plant tolerate stressful conditions. See Arteca,R. (1996), Plant Growth Substances. Principles and Applications. NewYork: Chapman & Hall; Mauseth, J. D. (1991), Botany: An Introduction toPlant Biology. Philadelphia: Saunders. pp. 348-415; Raven, P. H., Evert,R. F., and Eichhorn, S. E. (1992), Biology of Plants. New York: Worth.pp. 545-572.

Abscisic acid owes its name to the belief that this plant growthregulator causes the abscission of leaves from deciduous trees in thefall. Absicin II and dormin are names previously used for this planthormone. The chemistry and physiology of abscisic acid and its analogsis described by Milborrow, Ann. Rev. Plant Physiol. 1974, 25, 259-307.

Abscisic acid analogs are structural derivatives of2-cis-,4-trans-(S)-(+)-abscisic acid. An extensive series of analogs ofabscisic acid has been prepared by researchers at the PlantBiotechnology Institute of the National Research Council of Canada,Saskatoon, Saskatchewan. Some of these abscisic acid analogs aredisclosed in U.S. Pat. Nos. 5,201,931, 5,518,995 and 6,004,905, whichare incorporated herein by reference. Presently preferred abscisic acidanalogs include PBI-376, PBI-524, PBI-697 and PBI-410.

Prior art (U.K. Pat. No. 1251867 and Railton and Wareing, Planta 112,65-69, 1973) taught, inter alia, preparation of amine salts of racemicabscisic acid. A salt of racemic (R,S)-(±)-2-trans-,4-trans-abscisicacid with the chiral alkaloid brucine was prepared as a means ofresolving a small quantity of the racemate in order to study thephysical properties of its enantiomers (J. C. Bonnafous, et al.,Tetrahedron Letters, 1119-1122, 1973). Salts of (S)-(+)-abscisic acidare disclosed in a co-pending patent application Ser. No. ______,entitled SALTS, AQUEOUS LIQUID COMPOSITIONS CONTAINING SALTS OFS-(+)-ABSCISIC ACID, filed on the same day as this application. However,the prior art does not disclose salts of abscisic acid analogs withamines nor does it disclose alkali metal or alkaline earth salts ofabscisic acid analogs.

As noted above, abscisic acid analogs are carboxylic acids, and thus ina medium having an acidic pH, they are protonated and in their neutralundissociated form. This uncharged, undissociated form is morelipophilic than a salt of an abscisic acid analog s, and penetration ofthe uncharged acid form into the plant cuticle would be favored relativeto the charged, dissociated form of the abscisic acid analog present athigher pH (Blumenfeld and Bukovac 1972, Planta 107: 261-268). Theuncharged, undissociated form of the abscisic acid analog would beexpected to cross cell membranes from the apoplast into the cytosol moreeasily than a salt form would. In spite of this, we have surprisinglyfound that treatments comprising the salts of abscisic acid analogsdisclosed in this invention perform equally well or even slightly betterin biological activity when compared with similar treatments comprisingthe acid form of the same abscisic acid analog at the sameconcentration.

Abscisic acid was first defined in the early 1960s as a growth inhibitoraccumulating in abscising cotton fruit and in leaves of sycamore treesphotoperiodically induced to become dormant. See, Finkelstein R R, RockCD (2002), Abscisic Acid Biosynthesis and Response, The Arabidopsis BookVol. 45, No. 1 pp. 1-48. Since then, abscisic acid has been shown toregulate many aspects of plant growth and development, including embryomaturation, seed dormancy, germination, cell division and elongation,etc. Although abscisic acid has historically been thought of as a growthinhibitor, young tissues have high abscisic acid levels, and abscisicacid-deficient mutant plants are severely stunted because their abilityto reduce transpiration and establish turgor is impaired. Exogenousabscisic acid treatment of mutants restores normal cell expansion andgrowth.

Abscisic acid is thought to initiate its effects on cells throughbinding to receptor proteins, although their identities and locationsare still largely unknown. Activation of the putative receptor(s) causesa chain of events that results in rapid changes in ion channels andslower changes in the pattern of gene transcription. While manyindividual components of this chain of events have been identified, acomplete picture has not yet been obtained.

Commercial formulations comprising abscisic acid are used in agriculturefor various purposes, such as improving stress tolerance, slowing thegrowth rate, adjusting flowering phase, and other purposes. Abscisicacid has also been reported to possess insect inhibition qualities. SeeU.S. Pat. Nos. 4,434,180 and 4,209,530 to Visscher. Contents of thesepatents are herein incorporated by reference. Abscisic acid in apowdered form is currently commercially available from LomonBiotechnology Company, Ltd., a Chinese company, which markets it as asubstance that, among other uses, improves the yield and quality ofcrops.

However, one of the problems associated with preparation of formulationsis abscisic acid analogs is their relatively poor solubility in water:The solubilities of these compounds in water are even lower than that of(S)-(+)-abscisic acid itself, and for (S)-(+)-abscisic acid not morethan about 3 grams per liter or alternatively, less than 0.3% by weightwill dissolve at ordinary temperatures. Stated differently, aconcentration of about 3000 parts per million (ppm) is the highestconcentration of (S)-(+)-abscisic acid that can be achieved in purewater at room temperature, and the maximum for abscisic acid analogs iseven lower. While abscisic acid analogs have better solubility in someorganic solvents, liquid formulations of abscisic acid analogs inorganic solvents are unacceptable in some contexts because offlammability, toxicity, or pollution considerations. For example, theEnvironmental Protection Agency of the U.S. state of California iscurrently requiring that liquid formulations of agricultural productscontain no volatile organic solvent, and several other U.S. states areconsidering similar regulations. Nonvolatile organic solvents have thedetriment that, since they do not evaporate, they remain in theagricultural product as it impinges upon and is absorbed into the targetplant, with a probability of causing phytotoxicity and contaminatingfood products, since the amount of the solvent greatly exceeds theamount of active ingredient applied.

A further problem observed with concentrated solutions of abscisic acidanalogs in organic solvents is that it is difficult to prepare moredilute solutions by dilution into water without having a portion of theabscisic acid analog precipitate out in a gummy form that redissolvesonly very slowly and with great difficulty. This is of practicalimportance because a major use of abscisic acid analogs in agricultureor horticulture is for the reduction of transpiration in nursery plantsbeing prepared for transplantation or for sale to consumers, for whichpurpose the abscisic acid analog may be applied by means of an injectionsystem and automatic or hand applicators. The solution for use in suchan applicator must be a concentrate between about 50 and 100 times moreconcentrated than the dose rate that is actually reaching the plantswhen they are treated by foliar spray or drench. Thus for a typicalapplication to the nursery plants of 60 to 600 ppm, the concentrate mustcontain between 3000 and 60,000 ppm of (S)-(+)-abscisic acid in asolution that will mix instantly and completely with the water flowingthrough the hose, in such a way that there is no possibility offormation of a precipitate that would clog the nozzle through which thewater containing active ingredient is applied to the plants or thegrowing media of the plants. As explained above, the solubility ofabscisic acid analogs in water is less than 3000 ppm at ordinary ambienttemperature, so such an intermediate solution cannot practically beprepared in water. A solution of an abscisic acid analog in an organicsolvent cannot be used in such an injection applicator, becauseprecipitation of the active ingredient will occur during the mixing intothe water flowing in the system, and the spray nozzle will be clogged.Because of the solubility limitation, it is also not possible to providea liquid formulation of the abscisic acid analog in organic solvent at ahigher concentration (e.g. 10%) and then at the time of application toprepare an intermediate dilution in water to achieve the desiredconcentration of 3,000 to 60,000 ppm in the reservoir of the injectionapplicator.

An identical problem arises in the case of application of an abscisicacid analog to a vineyard, orchard, or agricultural field through anirrigation system, a practice commonly known as chemigation. Again, sucha system requires a concentrated solution of the active ingredient in aliquid solvent in such a form such that that solution is instantly andcompletely miscible with a stream of water flowing through theirrigation system. If any precipitation were to occur, it would blockthe nozzles (known as emitters) through which the water and dissolvedactive ingredient reach the target plants. Again in this situation aformulation consisting of an organic solution of the abscisic acidanalog would not be acceptable because of the problem of the low watersolubility.

While powdered formulations of abscisic acid analogs could be prepared,it is often more convenient to use concentrated liquid solutions insteadof powders. Therefore, there is an unmet need in the art for abscisicacid analog formulations comprising salts of abscisic acid analogs,which are much more soluble in water than the acids themselves are.

SUMMARY OF THE INVENTION

The present invention is generally directed to salts of abscisic acidanalogs.

In a further embodiment, the present invention is generally directed toaqueous compositions comprising an effective amount of a salt of ananalog of abscisic acid wherein the concentration of the salt is atleast about 0.5% by weight of the aqueous composition. Applicants haveunexpectedly discovered that salts of abscisic acid analogs allow fordramatic increases in solubility of abscisic acid analogs in water sothat concentrated solutions can be obtained. As a result of Applicants'invention, solutions can be obtained with abscisic acid analogconcentration as high as about 50% by weight. The present inventionallows for the creation of concentrated formulations of abscisic acidanalogs that are convenient for packaging, storage, transport andhandling, but must be diluted prior to use and specifically allows anyarbitrary intermediate dilution of these formulations to be made intowater without the risk of precipitation of the active ingredient.

Compositions of the present invention generally comprise the salt, anantimicrobial and a surfactant. Other components which enhance thelong-term storage stability of the composition or the biologicalactivity of the abscisic acid analog may optionally be included.

Some of the suitable salts of the invention include, but are not limitedto, the ammonium salt, the lithium, sodium, potassium, magnesium orcalcium salt, organic amine salts or mixtures comprising any number ofthese. In one embodiment, the organic amine salt is the triethanolaminesalt. In another embodiment, the organic amine salt is thedimethylethanolamine salt. In yet another embodiment, the organic aminesalt is the ethanolamine salt. These examples of salts are not limitingas other salts may also be suitable for use the present invention. Onepresently preferred salt is the ammonium salt.

The present invention is also directed to methods of preparation of theaqueous compositions comprising salts of abscisic acid analogs. In oneembodiment, the invention is directed to a method of preparation of theammonium salt of an abscisic acid analog comprising reacting theabscisic acid analog with a chemically equivalent amount of ammonia inaqueous solution. In another embodiment, the invention is directed to amethod of preparation of the lithium salt comprising reacting theabscisic acid analog with lithium hydroxide, lithium bicarbonate orlithium carbonate in aqueous solution. In another embodiment, theinvention is directed to a method of preparation of the sodium saltcomprising reacting the abscisic acid analog with a chemicallyequivalent amount of sodium hydroxide, sodium bicarbonate or sodiumcarbonate in aqueous solution. In another embodiment, the invention isdirected to a method of preparation of the potassium salt comprisingreacting the abscisic acid analog with a chemically equivalent amount ofpotassium hydroxide, potassium bicarbonate or potassium carbonate inaqueous solution. In another embodiment, the invention is directed to amethod of preparation of the magnesium salt comprising reacting theabscisic acid analog with one-half to one chemical equivalent ofmagnesium hydroxide, magnesium oxide, or magnesium carbonate or ahydrate thereof in aqueous solution or suspension. In anotherembodiment, the invention is directed to a method of preparation of thecalcium salt comprising reacting the abscisic acid analog with one-halfto one chemical equivalent of calcium hydroxide, calcium oxide orcalcium carbonate in aqueous solution or suspension. In yet anotherembodiment, the invention is directed to a method of preparation of anorganic amine salt comprising reacting the abscisic acid analog with onechemical equivalent of an organic amine in the presence or, if the amineis a liquid, in the absence of water.

A further embodiment of the invention includes mixtures comprisingcombinations of salts of the abscisic acid analog with an effectiveamount of a component or multiple components that enhance the long-termchemical stability of the analog and the mixture as a whole. Theseinclude but are not limited to citric acid or one of its water-solublesalts, sulfur dioxide or a water soluble bisulfite or sulfite salt.

A further embodiment of the invention includes mixtures comprisingcombinations of salts of abscisic acid analogs with a substantial amountof a component or multiple components which enhance the biologicalactivity of the abscisic acid analog, including but not limited to urea,ammonium nitrate, ammonium acetate, calcium chloride, magnesium nitrate,or a surfactant. Preferred surfactants are gel-forming constituents,such as members of the Brij family.

The disclosed embodiments are simply exemplary embodiments of theinventive concepts disclosed herein and should not be considered aslimiting, unless the claims expressly state otherwise.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to aqueous liquid compositions of salts ofabscisic acid analogs. Abscisic acid analogs are structural derivativesof 2-cis-,4-trans-(S)-(+)-abscisic acid, whose structure is set forthbelow:

The tertiary alcohol in these compounds typically defines a chiralcenter for the molecule so that (R)-, and (S)-structural variants orenantiomers as well as (R,S)-racemic mixtures are possible. The liquidcompositions of the present invention may utilize either the (R)-, or(S)-enantiomer or the (R,S)-racemic mixture of any selected abscisicacid analog.

For the purposes of this Application, abscisic acid analogs are definedby Structures 1, 2 and 3, wherein for Structure 1:

the bond at the 2-position of the side chain is a cis- or trans-doublebond,

the bond at the 4-position of the side chain is a trans-double bond or atriple bond,

the stereochemistry of the alcoholic hydroxyl group is S-, R- or anR,S-mixture,

the stereochemistry of the R₁ group is in a cis-relationship to thealcoholic hydroxyl group,

R₁=ethynyl, ethenyl, cyclopropyl or trifluoromethyl, and

For PBI-376, R₁ is ethenyl.

For PBI-524, R₁ is ethynyl.

For PBI-697, R₁ is cyclopropyl.

For Structure 2:

the bond at the 2-position of the side chain is a cis- or trans-doublebond,

the bond at the 4-position of the side chain is a triple bond,

the stereochemistry of the alcoholic hydroxyl group is S-, R- or anR,S-mixture,

For Structure 3:

the bond at the 2-position of the side chain is a cis- or trans-doublebond,

the bond at the 4-position of the side chain is a trans-double bond,

the stereochemistry of the alcoholic hydroxyl group is S-, R- or anR,S-mixture,

In one aspect, the present invention relates to an aqueous compositionfor the treatment of plants comprising an effective amount of a salt ofan analog of abscisic acid, wherein the concentration of the salt is atleast 0.5% by weight of said salt.

As used herein, all numerical values relating to amounts, weightpercentages and the like, are defined as “about” or “approximately” eachparticular value, namely, plus or minus 10%. For example, the phrase “atleast 5% by weight” is to be understood as “at least 4.5% to 5.5% byweight.” Therefore, amounts within 10% of the claimed values areencompassed by the scope of the claims.

The phrase “effective amount” of a salt means a sufficient amount of thesalt to provide the desired biological or chemical effect without at thesame time causing additional toxic effects. The amount of salt or otherformulation component that is “effective” will vary from composition tocomposition, depending on the particular agricultural use, theparticular salt or salts, and the like. Thus, it is not always possibleto specify an exact “effective amount.” However, an appropriate“effective amount” in any individual case may be determined by one ofordinary skill in the art using routine experimentation.

Liquid compositions of the present invention can be prepared as eitherready-to-use dilutions or dilutable concentrates. According to thepresent invention, a solution containing from 0.5% to as much as 50% byweight of abscisic acid analog can be obtained. The dilutableconcentrates can be diluted into water directly to a final applicationconcentration or to any intermediate dilution, without risk ofprecipitation of the active ingredient. The aqueous formulationsaccording to the present invention are inexpensive to manufacture, safeto handle and use, and the abscisic acid analog active ingredient isstable under storage and shipping conditions. With the compositions ofthe present invention there is no risk of fire as there might be withliquid formulations containing a flammable or combustible organicsolvent. There is no risk of contributing to the formation ofatmospheric pollution or smog as there is with formulations containing avolatile organic solvent. The aqueous formulations of the presentinvention are less toxic to humans or animals than similar formulationscontaining an organic solvent. A person having ordinary skill in the artwould be able to determine how to prepare the final aqueous solutionconcentration for direct application to plants, or how to prepare anyintermediate dilutions for use in chemigation equipment or injectiondiluters or similar equipment, without undue experimentation, withoutany chance of causing precipitation of the active ingredient, andwithout long and laborious stirring to bring the active ingredient intosolution.

The aqueous solution formulations of the present invention may alsooptionally include an effective amount of an additional ingredient orseveral additional ingredients in order to enhance the long-termchemical stability of the abscisic acid analog or of the formulation asa whole. Such enhancing ingredients include but are not limited tocitric acid or one of its water-soluble salts, sulfur dioxide or a watersoluble bisulfite or sulfite salt. The use of water as the solventallows for a combined liquid formulation comprising any or several ofthese inorganic components that may comprise a level of the enhancingingredient equal to the concentration of the abscisic acid analog saltor higher, if desired.

The aqueous solution formulations of the present invention may alsooptionally include a substantial amount of an additional ingredient orseveral additional ingredients in order to enhance the biologicalactivity of the abscisic acid analog. Such enhancing ingredients includebut are not limited to urea, ammonium nitrate, ammonium acetate, calciumchloride and magnesium nitrate. The use of water as the solvent allowsfor a combined liquid formulation comprising any or several of theseinorganic components or urea that may comprise a level of the enhancingingredient equal to the concentration of the abscisic acid analog saltor even up to 10 times the amount of abscisic acid analog by weight ormore. Again, this provides an advantage over the use of an organicsolvent, in which these inorganic components or urea have little if anysolubility.

Additionally, the aqueous solution formulations of the present inventionmay optionally include a substantial amount of a surfactant, in anamount equal by weight to the content of abscisic acid analog salt oreven several times greater. Examples of surfactants that may beincorporated into the compositions of the present invention include, butare not limited to products of the Brij family of polyoxyethylene fattyalcohol ethers (available from Uniquema, Castle Del.), products of theTween family of polyoxyethylene sorbitan esters (available fromUniquema, Castle Del.), products of the Silwet family of organosilicones(available from Union Carbide, Lisle Ill.), products of the Tritonfamily of alkylphenol ethoxylates (available from Dow Chemical Company,Midland Mich.), products of the Tomadol family of ethoxylated linearalcohols (available from Tomah3 Products, Inc., Milton Wis.), productsof the Myrj family of polyoxyethylene fatty acid esters (available fromUniquema Castle Del.), products of the Trylox family of ethoxylatedsorbitol and ethoxylated sorbitol esters (available from CognisCorporation, Cincinnati Ohio), or any of the specific commercialproducts Latron B-1956 (available from Rohm & Haas, Philadelphia Pa.),Capsil (available from Aquatrols, Paulsboro N.J.), Agral 90 (availablefrom Norac Concepts, Inc., Orleans ON, Canada), Kinetic (available fromSetre, Memphis Tenn.), or Regulaid (available from KALO, Overland ParkKans.). The presently preferred surfactants are those of the Brij orTween families. The most preferred surfactants for inclusion incompositions of the present invention are Brij 98, Brij 78, Tween 20 andTween 40. The concentration of surfactant in the compositions of theinvention may range from about 0.02% up to about 40%. The preferredrange of concentrations for the surfactant in the compositions of theinvention is from about 0.1% to 30%. The most preferred range ofconcentrations for the surfactant in the compositions of the inventionis from 0.5% to 25%. The surfactant may be included in the compositionsof the present invention either together with any one or more of theinorganic salt or urea activity enhancing ingredients or in the absenceof any of them.

The end user can apply compositions of the present invention to plantsfor various purposes, such as improving stress tolerance, reducing theirwater utilization, slowing their growth rate, adjusting flowering phase,for seed treatment, preventing preharvest fruit and flower drop andimproving the quality and color of fruits. The possible uses may alsoinclude, for example, distribution and sale of various concentratedsolutions of abscisic acid analogs. Utilizing such high concentrationsfor shipping and handling allows the use of smaller volumes of water,thus simplifying shipping and handling procedures and decreasing costs.The end user could then dilute the product to a 1% concentration (orother percentage depending on the end user's needs) and fill the supplyreservoir of mixing equipment for spray or drench application toornamental bedding plants ready for shipment. Alternatively, another enduser could prepare a diluted solution for injection into the dripirrigation system for a vineyard at the appropriate time to enhance thecolor or phenolic content of a wine or table grape crop.

Organic amine compounds that may be employed in the salts useful in thecompositions of the present invention are those containing one or twonitrogen atoms. If the amine compound contains one nitrogen atom, it mayinclude from one to six carbon atoms, from zero to three oxygen atomsand zero to four degrees of unsaturation, where a degree of unsaturationis defined as a carbon-carbon multiple bond or a ring in a cyclicstructure. If the amine compound contains two nitrogen atoms, it mayinclude from two to ten carbons, zero to four oxygen atoms and zero tofour degrees of unsaturation. These organic amine compounds include, butare not limited to methylamine, ethylamine, propylamine, isopropylamine,dimethylamine, diethylamine, trimethylamine, triethylamime,ethanolamine, N-methylethanolamine, N,N-dimethylethanolamine,diethanolamine, triethanolamine, ethylenediamine,tetramethylethylenediamine, and other similar compounds.

In another aspect, the present invention relates to methods ofpreparation of the aqueous compositions comprising salts of abscisicacid analogs. For example, in one embodiment, the invention is directedto a method of preparation of the ammonium salt of abscisic acidcomprising reacting the abscisic acid analog with ammonia. In anotherembodiment, the invention is directed to a method of preparation of thepotassium salt, comprising reacting the abscisic acid analog withpotassium hydroxide. In yet another embodiment, the invention isdirected to a method of preparation of the organic amine salt comprisingreacting the abscisic acid analog with the organic amine.

In a preferred embodiment, at least about 0.25% by weight of Tween-20, adetergent polysorbate, is added to the reaction mixture and resultingformulation when preparing the abscisic acid analog salts.

In another preferred embodiment, the aqueous solution comprises anantimicrobial agent to prevent microbial growth during long-termstorage. The presently most preferred antimicrobial agent is potassiumsorbate. When the aqueous solution of an abscisic acid analog salt ofthe present invention is intended for long term storage or fordistribution and commercial sale to the user, it is advantageous toincorporate the antimicrobial agent at a concentration of from 0.01% to1.0% by weight.

In another preferred embodiment, the aqueous solution comprises an agentto prevent undesirable development of coloration or appearance ofprecipitate during long-term storage. The presently most preferredagents for this purpose are sodium or potassium citrate and sodium orpotassium sulfite or bisulfite.

In the preferred embodiments, the pH of the concentrated compositions ofthe invention and any aqueous solutions at final use dilution preparedfrom the concentrates are both approximately neutral (near pH 7).

Preferred compositions of the present invention comprise from 0.5 to 50weight % of abscisic acid analog in the form of a salt, from 0.01 to 1.0weight % of an antimicrobial agent, optionally from 0.01 to 5% of astability enhancing agent, optionally from 0.25 to 35 weight % of asurfactant, optionally from 1 to 50 weight % of another activityenhancing component, with the balance being water.

The following examples are intended to illustrate the present inventionand to teach one of ordinary skill in the art how to make and use theinvention. They are not intended to limit the invention or itsprotection in any way.

EXAMPLES Example 1 Preparation of an Aqueous Solution Composition of theAmmonium Salt of (S)-(+)-abscisic acid comprising potassium sorbate

In a 600 mL beaker, 55 g of (S)-(+)-abscisic acid of 95% purity wasadded, followed by 500 μL of Tween 20 and 200 mL of water. Then, 10 mLof concentrated aqueous ammonia were added while stirring until themixture came to equilibrium. Then, additional concentrated ammonia wasadded dropwise until all solid was dissolved. A homogenous solution wasachieved when a total of about 13.5 mL of ammonia has been added. Atthis point, potassium sorbate (1.25 g) was added to the composition; itquickly dissolved. The mixture was transferred to a 500 ml volumetricflask and was brought up to 500 mL with deionized water. The mixture wasstored in a brown glass bottle. The pH was measured to be 6.50.

Thus an aqueous solution composition comprising 10% abscisic acid as theammonium salt by weight, and further comprising a naturally-occurringantimicrobial preservative, was prepared.

Example 2 Preparation of an Aqueous Solution Composition of the AmmoniumSalt of Abscisic Acid Analog PBI-524 Comprising Potassium Sorbate

A weight of 1.09 g of abscisic acid analog PBI-524 was combined with 20mg of Tween-20 and 50 mg of potassium sorbate in 10 mL of water andstirred for a few minutes to achieve a smooth suspension. Ammonia wasadded in the form of a 1+9 dilution of commercial concentrated productas a titration to bring all of the solid into solution. The mixture wasmade up on a balance to a total weight of 20 g by adding water, and itwas transferred to a brown bottle for storage.

Thus, an aqueous solution composition was prepared comprising 5% byweight abscisic acid analog PBI-524 as the ammonium salt, and furthercomprising a naturally-occurring antimicrobial preservative.

Example 3 Preparation of an Aqueous Solution Composition of the AmmoniumSalt of Abscisic Acid Analog PBI-524 Comprising Potassium Sorbate,Sodium Citrate and Sodium Metabisulfite

A solution was prepared comprising 50 mg potassium sorbate, 20 mg ofTween-20, 100 mg of trisodium citrate dihydrate and 50 mg of sodiummetabisulfite in 10 mL of water. After adding 1.09 g of abscisic acidanalog PBI-524 the mixture was stirred for a few minutes to achieve ahomogeneous suspension. Ammonia was added in the form of a 1+9 dilutionof commercial concentrated product as a titration to bring all of thesolid into solution. The mixture was made up on a balance to a totalweight of 20 g by adding water, and it was transferred to a brown bottlefor storage.

Thus, an aqueous solution composition was prepared comprising 5% byweight abscisic acid analog PBI-524 as the ammonium salt, and furthercomprising sodium citrate, sodium bisulfite and a naturally-occurringantimicrobial preservative.

Preparation of plant specimens for use in the treatment studies ofExample 4 that follows was carried out as follows. Tomato (variety:Rutgers) seeds were sown in an 18-cell flat filled with Promix PGX(available from Premier Horticulture Inc., Quakertown Pa.) and grown for3 weeks to allow for germination and initial growth. Plants were thentransplanted into pots (18 cm in diameter and 18 cm in height), filledwith Promix BX (available from Premier Horticulture Inc., QuakertownPa.), and grown for one or two more weeks before treatment, depending ontemperature and available light. Plants received daily irrigation andweekly fertilizer (1 g/L all purpose fertilizer 20-20-20, available fromThe Scotts Company, Marysville, Ohio).

All treatment solutions were made up with distilled water. The(S)-(+)-abscisic acid (95% active ingredient) is available from LomonBioTechnology Co., Ltd. (Shichuan, China). Twenty L of a 250 ppmsolution of (S)-(+)-abscisic acid was prepared and stored in the dark at20-25° C. This same 250-ppm (S)-(+)-abscisic acid solution was used as acontrol for all studies to eliminate the possibility of applying anincorrect concentration.

The experiment was conducted using a randomized complete blockexperimental design. Solutions of (S)-(+)-abscisic acid and blanktreatments (plain water) were applied by spray to the aerial parts ofthe tomato plants at the rate of 20 mL per 6 plants. Plants were thenplaced in a transparent chamber with humidity controlled within therange of 40 to 60% relative humidity. Leaf transpiration rates weremeasured at 1, 2, 3, 4 and 7 days after treatment. Measurements wereconducted using a LI-1600 Steady State Porometer (LI-Cor, Lincoln,Nebr.). Each day the transpiration rate of the plants of each treatmentgroup was normalized to a percentage of the transpiration rate ofuntreated plants (plants sprayed with water only) in order to controlfor day-to-day variability in plant status caused by changes ofenvironmental conditions such as light intensity and temperature. Dataof each plant was also averaged over a 3-day period to balance the shortterm and long term effect of (S)-(+)-abscisic acid on tomato leaftranspiration as well as to reduce experimental variability.

Example 4

The effect of abscisic acid analog PBI-524, in comparison with theeffects of the abscisic acid analog ammonium salts of the presentinvention, as prepared in the Examples 2 and 3 was studied in an assaymeasuring tomato leaf transpiration rate (Table 1). The aqueous solutioncompositions of the Examples were each diluted with water to a finalapplication concentration of 25 ppm (based on abscisic acid analogcontent) to match the abscisic acid analog (non-salt) standardtreatment.

TABLE 1 Effect of abscisic acid analog ammonium salt with or withoutBrij 98 on tomato leaf transpiration compared to the effect of theabscisic acid analog itself. Transpiration rate (% of control) Daysafter treatment Treatment 1 2 3 4 7 Average Untreated control (wateronly) 100.00 100.00 100.00 100.00 100.00 100.00 Positive control (250ppm (S)-(+)- 48.47 75.50 78.06 82.73 97.51 76.46 abscisic acid saltcomposition of Example 1 = 1 mg/plant) Surfactant control (250 ppm (S)-23.63 39.53 56.96 63.95 85.07 53.83 (+)-abscisic acid salt compositionof Example 1 + 0.05% Brij 98) 25 ppm PBI-524 93.31 84.64 88.95 71.4491.50 85.97 25 ppm PBI-524 + 0.05% Brij 98 48.41 52.45 54.63 51.55 84.8658.38 25 ppm abscisic acid analog salt 87.34 75.59 81.30 70.98 91.5581.35 composition of Example 2 25 ppm abscisic acid analog salt 39.0352.77 56.28 51.10 82.74 56.39 composition of Example 2 + 0.05% Brij 9825 ppm abscisic acid analog salt 82.25 84.35 80.69 71.09 92.73 82.22composition of Example 3 25 ppm abscisic acid analog salt 49.73 51.9851.94 53.66 81.66 57.79 composition of Example 3 + 0.05% Brij 98

Thus it has been demonstrated that the ammonium salt compositions ofabscisic acid analog BPI-524 of the present invention are at least asefficacious biologically as the abscisic acid analog PBI-524 itself is.

1. A salt or mixture of salts of an analog of abscisic acid.
 2. The saltof claim 1, wherein said salt is the ammonium salt.
 3. The salt of claim1, wherein said salt is the sodium salt.
 4. The salt of claim 1, whereinsaid salt is the potassium salt.
 5. The salt of claim 1, wherein saidsalt is the lithium, magnesium or calcium salt.
 6. The salt of claim 1,wherein said salt comprises ammonium and potassium salts in a nitrogento potassium weight ratio between 1:20 and 20:1.
 7. The salt of claim 1,wherein said salt is an organic amine salt.
 8. The salt of claim 7,wherein said organic amine salt contains one or two nitrogen atoms. 9.The salt of claim 7, wherein said organic amine salt is thetriethanolamine salt.
 10. The salt of claim 7, wherein said organicamine salt is the dimethylethanolamine salt.
 11. The salt of claim 7,wherein said organic amine salt is the ethanolamine salt.
 12. An aqueouscomposition for treatment of plants comprising an effective amount of atleast one salt of an abscisic acid analog, wherein the concentration ofthe salt is at least 0.5% by weight of said composition, an effectiveamount of an antimicrobial agent, an effective amount of a surfactant,optionally one or more performance enhancing additives and optionallyone or more additives to stabilize the color.
 13. The composition ofclaim 12, wherein the concentration of the salt is at least 2% by weightof said composition.
 14. The composition of claim 12 that furthercomprises an antimicrobial agent.
 15. The composition of claim 12,wherein said antimicrobial agent is potassium sorbate.
 16. Thecomposition of claim 12 that further comprises a performance-enhancingadditive.
 17. The composition of claim 16 wherein saidperformance-enhancing additive is selected from the group consisting ofammonium nitrate; calcium chloride; and magnesium nitrate.
 18. Thecomposition of claim 12 that further comprises one or more additives tostabilize the color.
 19. The composition of claim 18 wherein saidcolor-stabilizing additive is a sodium or potassium salt of citric acidor sodium or potassium sulfite, bisulfite or metabisulfite.
 20. Anaqueous composition that comprises from about 5 to about 45 weight % of(S)-(+)-abscisic acid as the ammonium salt and from about 0.1 to about0.5 weight % potassium sorbate.